Browsing by Author "Hsiao, Yu-Tang"

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Fluorinated heptacyclic carbazole-based ladder-type acceptors with aliphatic side chains for efficient fullerene-free organic solar cells
(2019-05-01)
Chen, Tsung-Wei
;
Hsiao, Yu-Tang
;
Lin, You-Wei
;
Chang, Chia-Chih
;
Chuang, Wei-Tsung
Molecular engineering of non-fullerene acceptors (NFAs) is a promising strategy to uncover new structure-property relationships and design principles for developing next-generation high performance n-type materials. Two dithienocyclopentacarbazole (DTC)-based NFAs, DTC(4R)-IC and DTC(4R)-4FIC, are synthesized to elucidate the effects of incorporating aliphatic side chains and 2-(5,6-difluoro-3-oxo-2,3-dihydro-1H-inden-1-ylidene)malononitrile (2FIC) end groups on the thermal and optoelectronic properties of these NFAs. An inverted organic solar cell architecture of ITO/ZnO/J71:NFA/MoO3/Ag is employed. By replacing the phenyl-based side chains with aliphatic side chains on the carbon bridges of the carbazole-based core, the device containing DTC(4R)-IC exhibits an enhanced PCE of 9.61%, a V-OC of 0.94 V, a J(SC) of 16.44 mA cm(-2), and a FF of 62.00%, whereas the device containing DTC(4Ph)-IC exhibits a PCE of 7.76%. The incorporation of 2FIC end groups affords DTC(4R)-4FIC featuring better device performance relative to DTC(4R)-IC, a more red-shifted absorption edge, and a broader absorption range upon fluorination. Notably, the device fabricated with DTC(4R)-4FIC affords a V-oc of 0.82 V, a J(sc) of 18.92 mA cm(-2), a FF of 70.22% and a highest PCE of 10.89%, which is by far the highest PCE for NFA containing heptacyclic carbazole cores.
Haptacyclic Carbazole-Based Ladder-Type Nonfullerene Acceptor with Side-Chain Optimization for Efficient Organic Photovoltaics
(2017-12-06)
Hsiao, Yu-Tang
;
Li, Chia-Hua
;
Chang, Shao-Ling
;
Heo, Soowon
;
Tajima, Keisuke
In this research, a haptacyclic carbazole-based dithienocyclopentacarbazole (DTCC) ladder-type structure was formylated to couple with two 1,1-dicyanomethylene-3-indanone (IC) moieties, forming a new nonfullerene acceptor DTCCIC-C17 using a bulky branched 1-octylnonayl side chain at the nitrogen of the embedded carbazole and four 4-octylphenyl groups at the sp(3)-carbon bridges. The rigid and coplanar main-chain backbone of the DTCC core provides a broad light-absorbing window and a higher-lying LUMO energy level, whereas the bulky flanked side chains reduce intermolecular interactions, making DTCCIC-C17 amorphous with excellent solution processability. The DTCCIC-C17 as an acceptor is combined with a medium band gap polymer poly[(2,6-(4,8-bis(5-(2-ethylhexyl)thiophen-2-y1)-benzo[1,2-b:4,5-bldithiophene))-alt-(5,5-(1',3'-di-2-thieny1-5',7'-bis(2-ethylhexyl)benzo[1',2'-c:4',5'-c']dithiophene-4,8-dione))] (PBDB-T) as the donor in the active layer to obtain suitable highest occupied molecular orbital/lowest unoccupied molecular orbital energy alignments and complimentary absorption. The devices with an inverted configuration (ITO/ZnO/active layer/MoO3/Ag) without using an aqueous poly(3,4-ethylenedioxythiophene) polystyrene sulfonate layer were fabricated for better device stability. When the diiodooctane-treated PBDB-T:DTCCIC-C17 active layer was thermally annealed at 50 degrees C for 10 min, the device achieved the highest efficiency of 9.48% with a high V-oc of 0.98 V, a J(sc) of 14.27 mA cm(-2), and an FF of 0.68.
Single-Junction Organic Solar Cell Containing a Fluorinated Heptacyclic Carbazole-Based Ladder-Type Acceptor Affords over 13% Efficiency with Solution-Processed Cross-Linkable Fullerene as an Interfacial Layer
(2019-08-28)
Chen, Tsung-Wei
;
Chang, Chia-Chih
;
Hsiao, Yu-Tang
;
Chan, ChoonKee
;
Hong, Ling
In this article, a fluorinated heptacyclic dithienocyclopentacarbazole (DTC)-based non-fullerene acceptor (NFA), DTC(4Ph)-4FIC, is synthesized and blended with J71, PBDB-T, and PBDB-TF, featuring complementary absorption and well-matched energy levels. The DTC(4Ph)-4FIC neat film exhibits face-on preference, whereas the nonfluorinated counterpart, DTC(4Ph)-IC, exhibits edge-on preference; this unique feature owing to fluorination in DTC-based NFAs is observed for the first time. More importantly, DTC(4Ph)-4FIC exhibits improved power conversion efficiencies (PCEs) of 10.92 and 10.41% in J71- and PBDB-T-containing devices, while the devices that employed DTC(4Ph)-IC afford PCEs of 7.76 and 9.48%, respectively. Because PBDB-TF is known to exhibit lower energy levels than J71 and PBDB-T, the corresponding device affords a V-OC of 0.95 V, a J(SC) of 18.29 mA cm(-2), a FF of 75.70%, and a PCE of 13.15%, which is 20 and 26% higher than J71- and PBDB-T-containing devices. Furthermore, the inverted device containing the PBDB-TF:DTC(4Ph)-4FIC blend is fabricated using cross-linkable fullerene (C-PCBSD) as the cathode interlayer, affording a decent PCE of 13.36%, with a V-OC of 0.94 V, a J(SC) of 20.20 mA cm(-2), and a FF of 70.42%.